Вправа 6.45 гдз 7 клас алгебра Біляніна Білянін Андрух

№ 6.45
Знайти розв'язок системи рівнянь. $$
\begin{aligned}
& \text { a) } \begin{array}{l}
4 \cdot(x+y)=8 y-4, \\
7 \bullet(y+1)=22+y ;
\end{array} \\
& \left\{\begin{array}{l}
4 x+4 y=8 y-4, \\
7 y+7=22+y,
\end{array}\right. \\
& \left\{\begin{array}{l}
4 x+4 y-8 y=-4, \\
7 y-y=22-7,
\end{array}\right. \\
& \left\{\begin{array}{l}
4 x-4 y=-4, \\
6 y=15,
\end{array}\right. \\
& \left\{\begin{array}{l}
x-y=-1, \\
y=2,5,
\end{array}\right. \\
& \left\{\begin{array}{l}
x=y-1, \\
y=2,5,
\end{array}\right. \\
& \left\{\begin{array}{l}
x=2,5-1, \\
y=2,5,
\end{array}\right. \\
& \left\{\begin{array}{l}
x=1,5, \\
y=2,5
\end{array}\right. \\
& \text { б) }\left\{\begin{array}{l}
9 \cdot(x-2 y)-6 x=-11, \\
8-(x+y)=6 y+4 .
\end{array}\right. \\
& \left\{\begin{array}{l}
x-18 y-6 x=-11, \\
8 x+8 y=6 y+4,
\end{array}\right. \\
& \left\{\begin{array}{l}
3 x-18 y=-11, \\
8 x+8 y-6 y=4,
\end{array}\right. \\
& \left\{\begin{array}{l}
3 x-18 y=-11, \\
8 x+2 y=4,
\end{array}\right.
\end{aligned}
$$
\begin{aligned}
&\begin{aligned}
& \left\{\begin{array}{l}
3 x-18 \cdot(2-4 x)=-11 \\
y=2-4 x
\end{array}\right. \\
& \left\{\begin{array}{l}
3 x-36+72 x=-11 \\
y=2-4 x
\end{array}\right. \\
& \left\{\begin{array}{l}
75 x=25 \\
y=2-4 x
\end{array}\right. \\
& \left\{\begin{array}{l}
x=\frac{1}{3} \\
y=2-\frac{4}{3}
\end{array}\right. \\
& \left\{\begin{array}{l}
x=\frac{1}{3} \\
y=\frac{2}{3}
\end{array}\right.
\end{aligned}\\
&\text { Відповідь: а) }(1,5 ; 2,5) \text {, б) }\left(\frac{1}{3} ; \frac{2}{3}\right) \text {. }
\end{aligned}